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Small, Low Power, 3-Axis±3 g

A cc e l e r o m e t e r AD X L 335

FEATURES

3-axis sensingSmall, low profile package4 mm × 4 mm × 1.45 mm

LFCSP Low power : 350 μA (typical)Single-supply operation: 1.8 V to 3.6V 10,000 g shock survivalExcellent temperature stabilityBW adjustment with a single capacitor per axis RoHS/WEEE lead-free compliant

APPLICATIONSCost sensitive, low power, motion- and tilt-

sensing applicationsMobile devices Gaming systems Disk drive protectionImage stabilizationSports and health devices

GENERAL DESCRIPTION

The ADXL335 is a small, thin, low power, complete 3-axis accel-erometer with signal conditioned voltage outputs. The product measures acceleration with a minimum full-scale rangeof ±3 g. It can measure the static acceleration of gravity in tilt-sensing applications, as well as dynamic acceleration resulting from motion, shock, or vibration.

The user selects the bandwidth of the accelerometer using theCX, CY, and CZ capacitors at the XOUT, YOUT, and ZOUT pins. Bandwidths can be selected to suit the application, with a range of 0.5 Hz to 1600 Hz for the X and Y axes, and a range of 0.5 Hz to 550 Hz for the Z axis.

The ADXL335 is available in a small, low profile, 4 mm ×4 mm × 1.45 mm, 16-lead, plastic lead frame chip scale package(LFCSP_LQ).

FUNCTIONAL BLOCK DIAGRAM+3V

CDC

XOUTADXL335OUTPUT AMP

~32kΩ

3-AXISSENSOR

OUAC AMP DEMOD OUTPUT AMP

~32kΩ

TOUOUTPUT AMP

~32kΩ

COM ST

Figure 1.

Rev. 0Information furnished by Analog Devices is believed to be accurate and reliable.However, no responsibility isassumed byAnalog Devices for its use,nor for anyinfringements ofpatents or other rights ofthirdparties that may result fromits use.Specifications subject to change without notice. No license is grantedbyimplicationor otherwise under anypatent or patent rights of Analog Devices. Trademarks andregisteredtrademarks arethe property oftheir respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.Tel: 781.329.4700 www.analog.com

ADXL335

TABLE OF CONTENTSFeatures .............................................................................................. 1

Applications .......................................................................................

1 General Description

......................................................................... 1 Functional Block

Diagram .............................................................. 1 Revision History

............................................................................... 2 Specifications

..................................................................................... 3 Absolute

Maximum Ratings............................................................ 4 ESD

Caution .................................................................................. 4 Pin

Configuration and Function Descriptions............................. 5

Typical Performance Characteristics .............................................

6 Theory of Operation ......................................................................

Mechanical Sensor...................................................................... 10

Performance ................................................................................ 10

Applications Information ..............................................................

11 Power Supply Decoupling .........................................................

11 Setting the Bandwidth Using CX, CY, and CZ ..........................

11 Self Test ........................................................................................

Design Trade-Offs for Selecting Filter Characteristics:The Noise/BW Trade-Off .......................................................... 11

Use with Operating Voltages Other than 3 V.............................

11 Axes of Acceleration Sensitivity ...............................................

12 Layout and Design Recommendations ...................................

13 Outline Dimensions .......................................................................

Ordering Guide .......................................................................... 14

REVISION HISTORY 1/09—Revision 0: Initial Version

Rev. 0 | Page 2 of 16

ADXL335

SPECIFICATIONSTA = 25°C, VS = 3 V, CX = CY = CZ = 0.1 μF, acceleration = 0 g, unless otherwise noted. All minimum and maximum specifications are guaranteed. Typical specifications are not guaranteed.

Table 1.

Parameter Conditions Min Typ Max Unit

SENSOR INPUT Measurement RangeNonlinearityPackage Alignment ErrorInteraxis AlignmentError Cross-AxisSensitivity1

Each axis

% of full scale

±3 ±3.6 ±0.3 ±1 ±0.1 ±1

g%DegreesDegrees%

SENSITIVITY (RATIOMETRIC)2

Sensitivity at XOUT, YOUT, ZOUT

Each axisVS = 3 V VS = 3 V

270 300 330 ±0.01

mV/g%/°C

ZERO g BIAS LEVEL (RATIOMETRIC)0 g Voltage at XOUT, YOUT

0 g Voltage at ZOUT

0 g Offset vs. Temperature

VS = 3 VVS = 3 V

1.35 1.5 1.65 1.2 1.5 1.8

±1

VVmg/°C

NOISE PERFORMANCE Noise Density XOUT, YOUT

Noise Density ZOUT

150300

μg/√Hz rmsμg/√Hz rms

FREQUENCY RESPONSE4

Bandwidth XOUT, YOUT5

Bandwidth ZOUT5

RFILT ToleranceSensor Resonant Frequency

No external filter

1600

550

32 ± 15%5.5

HzHzkΩkHz

SELF-TEST6

Logic Input LowLogic Input HighST Actuation Current Output Change at XOUT

Output Change at YOUT

Output Change at ZOUT

Self-Test 0 to Self-Test1 Self-Test 0 to Self-Test 1 Self-Test 0 toSelf-Test 1

+0.6+2.4+60

−150 −325 −600+150 +325 +600+150 +550 +1000

V V μA mV mV mV

OUTPUT AMPLIFIER Output Swing Low Output Swing High

No loadNo load

0.12.8

POWER SUPPLYOperating Voltage RangeSupply Current

Turn-On Time7

VS = 3 V

No external filter

1.8 3.6 3501

V μA ms

TEMPERATUREOperating Temperature Range −40 +85 °C

1 Defined as coupling between any two axes. 2 Sensitivity is essentially ratiometric to VS.3 Defined as the output change from ambient-to-maximum temperature or ambient-to-minimum temperature. 4 Actual frequency response controlled by user-supplied external filter capacitors (CX, CY, CZ).5 Bandwidth with external capacitors = 1/(2 × π × 32 kΩ × C). For CX, CY = 0.003 μF, bandwidth = 1.6 kHz. For CZ = 0.01 μF, bandwidth = 500 Hz. For CX, CY, CZ =

10 μF, bandwidth = 0.5 Hz.6 Self-test response changes cubically with VS.7 Turn-on time is dependent on CX, CY, CZ and is approximately 160 × CX or CY or CZ + 1 ms, where CX, CY, CZ are in microfarads (μF).

Rev. 0 | Page 3 of 16

ADXL335

ABSOLUTE MAXIMUM RATINGSTable 2.Parameter Rating

Acceleration (Any Axis, Unpowered) Acceleration (Any Axis, Powered) VS

All Other PinsOutput Short-Circuit Duration

(Any Pin to Common)Temperature Range (Powered)Temperature Range (Storage)

10,000 g10,000 g−0.3 V to +3.6 V (COM − 0.3 V) to (VS + 0.3 V) Indefinite

−55°C to +125°C−65°C to +150°C

Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods mayaffect device reliability.

ESD CAUTION

Rev. 0 | Page 4 of 16

ADXL33

5 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS16 15 14 13

NC 1 ADXL335 12TOP VIEW

ST 2(Not to Scale)

11+Y

COM 3 +Z 10

XOUT

YOUT

NC 4 +X 9 NC5 6 7 8

NC = NO CONNECT

NOTES1. EXPOSED PAD IS NOT INTERNALLY CONNECTED BUT SHOULD BE SOLDERED FOR MECHANICAL INTEGRITY.

Figure 2. Pin Configuration

Table 3. Pin Function Descriptions

Pin No. Mnemonic Description

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 EP

NC ST COM NC COM COM COM ZOUT

NC YOUT

NC XOUT

NC VS

NCExposed Pad

No Connect1.Self-Test. Common. No Connect1.Common. Common. Common.Z Channel Output.No Connect1.Y Channel Output.No Connect1.X Channel Output.No Connect1.Supply Voltage (1.8 V to 3.6V). Supply Voltage (1.8 V to3.6 V). No Connect1.Not internally connected. Solder for mechanical integrity.

1NC pins are not internally connected and can be tied to COM pins, unless otherwise noted.

Rev. 0 | Page 5 of 16

ADXL335

TYPICAL PERFORMANCE CHARACTERISTICS N > 1000 for all typical performance plots, unless otherwise noted.

50 40

4030

10 10

01.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58

0–0.40 –0.38 –0.36 –0.34 –0.32 –0.30 –0.28 –0.26

OUTPUT (V)

Figure 3. X-Axis Zero g Bias at 25°C, VS = 3V

VOLTS (V)

Figure 6. X-Axis Self-Test Response at 25°C, VS = 3 V

50 50

40 40

30 30

20 20

10 10

01.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58

00.26 0.28 0.30 0.32 0.34 0.36 0.38 0.40

OUTPUT (V)

Figure 4. Y-Axis Zero g Bias at 25°C, VS = 3 V

VOLTS (V)

Figure 7. Y-Axis Self-Test Response at 25°C, VS = 3 V

25 40

2030

10 5

01.42 1.44 1.46 1.48 1.50 1.52 1.54 1.56 1.58

00.48 0.50 0.52 0.54 0.56 0.58 0.60 0.62

OUTPUT (V)

Figure 5. Z-Axis Zero g Bias at 25°C, VS = 3 V

VOLTS (V)

Figure 8. Z-Axis Self-Test Response at 25°C, VS = 3 V

Rev. 0 | Page 6 of 16

ADXL335

0–3.0 –2.5 –2.0 –1.5 –1.0 –0.5 0 0.5 1.0 1.5 2.0 2.5 3.0

1.55

1.54

1.53

1.52

1.51

1.50

1.49

1.48

1.47

1.46

1.45–40 –30 –20 –10 0 10 20 30 40 50 60 70 80 90 100

TEMPERATURE COEFFICIENT (mg/°C)

Figure 9. X-Axis Zero g Bias Temperature Coefficient, VS = 3

N = 8

TEMPERATURE (°C)

Figure 12. X-Axis Zero g Bias vs. Temperature— Eight Parts Soldered to PCB

1.55N = 8

1.54

1.53

1.52

1.51

1.50

1.49

1.48

1.47

1.46

0–3.0 –2.5 –2.0 –1.5 –1.0 –0.5 0 0.5 1.0 1.5 2.0 2.5 3.0

1.45–40 –30 –20 –10 0 10 20 30 40 50 60 70 80 90 100

TEMPERATURE COEFFICIENT (mg/°C)

Figure 10. Y-Axis Zero g Bias Temperature Coefficient, VS = 3V

TEMPERATURE (°C)

Figure 13. Y-Axis Zero g Bias vs. Temperature— Eight Parts Soldered to PCB

1.50N = 8

1.48

1.46

1.44

1.42

1.40

1.38

1.36

1.34

1.32

0–7 –6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6 7

1.30–40 –30 –20 –10 0 10 20 30 40 50 60 70 80 90 100

TEMPERATURE COEFFICIENT (mg/°C)

Figure 11. Z-Axis Zero g Bias Temperature Coefficient, VS = 3 V

TEMPERATURE (°C)

Figure 14. Z-Axis Zero g Bias vs. Temperature— Eight Parts Soldered to PCB

Rev. 0 | Page 7 of 16

ADXL335

20 0.320

0.315

15 0.310

0.305

10 0.300

0.295

5 0.290

0.285

00.285 0.288 0.291 0.294 0.297 0.300 0.303 0.306 0.309 0.312 0.315

SENSITIVITY (V/g)

0.280–40 –30 –20 –10 0

10 20 30 40 50 60 70 80 90 100

TEMPERATURE (°C)

Figure 15. X-Axis Sensitivity at 25°C, VS = 3 V Figure 18. X-Axis Sensitivity vs. Temperature— Eight Parts Soldered to PCB, VS = 3 V

00.285 0.288 0.291 0.294 0.297 0.300 0.303 0.306 0.309 0.312 0.315

SENSITIVITY (V/g)

0.320

0.315

0.310

0.305

0.300

0.295

0.290

0.285

0.280–40 –30 –20 –10 0

10 20 30 40 50 60 70 80 90 100

TEMPERATURE (°C)

N = 8

Figure 16. Y-Axis Sensitivity at 25°C, VS = 3 V Figure 19. Y-Axis Sensitivity vs. Temperature— Eight Parts Soldered to PCB, VS = 3 V

25 0.320

0.315

200.310

00.285 0.288 0.291 0.294 0.297 0.300 0.303 0.306 0.309 0.312 0.315

SENSITIVITY (V/g)

0.305

0.300

0.295

0.290

0.285

0.280–40 –30 –20 –10 0

10 20 30 40 50 60 70 80 90 100

TEMPERATURE (°C)

Figure 17. Z-Axis Sensitivity at 25°C, VS = 3 V Figure 20. Z-Axis Sensitivity vs. Temperature— Eight Parts Soldered to PCB, VS = 3 V

Rev. 0 | Page 8 of 16

N = 8

ADXL335

600

500

400

300

200

100

01.5 2.0 2.5 3.0 3.5 4.0

TIME (1ms/DIV)

SUPPLY (V)

Figure 21. Typical Current Consumption vs. Supply Voltage Figure 22. Typical Turn-On Time, VS = 3 V

CH4:500m

ZOUT,V/DIV

,CH3: YOUT500mV/DIV

,CH2: XOUT500mV/DIV

CH1: POWER,

1V/DIVOUTPUTS E FSET FOR CLARIT

Rev. 0 | Page 9 of 16

ADXL335

THEORY OF OPERATIONThe ADXL335 is a complete 3-axis acceleration measurement

system. The ADXL335 has a measurement range of ±3 g mini-mum. It contains a polysilicon surface-micromachined sensorand signal conditioning circuitry to implement an open-loop acceleration measurement architecture. The output signals areanalog voltages that are proportional to acceleration. The accelerometer can measure the static acceleration of gravityin tilt-sensing applications as well as dynamic accelerationresulting from motion, shock, or vibration.

The sensor is a polysilicon surface-micromachined structure built on top of a silicon wafer. Polysilicon springs suspend the structure over the surface of the wafer and provide a resistance against acceleration forces. Deflection of the structure is meas-ured using a differential capacitor that consists of independent fixed plates and plates attached to the moving mass. The fixed plates are driven by 180° out-of-phase square waves. Acceleration deflects the moving mass and unbalances the differential capacitor resulting in a sensor output whose amplitude is proportional to acceleration. Phase-sensitive demodulation techniques are then used to determine the magnitude and direction of theacceleration.

The demodulator output is amplified and brought off-chip through a 32 kΩ resistor. The user then sets the signal bandwidth of the device by adding a capacitor. This filtering improves measurement resolution and helps prevent aliasing.

MECHANICAL SENSOR

The ADXL335 uses a single structure for sensing the X, Y, and Z axes. As a result, the three axes’ sense directions are highly orthogonal and have little cross-axis sensitivity. Mechanical misalignment of the sensor die to the package is the chief source of cross-axis sensitivity. Mechanical misalignmentcan, of course, be calibrated out at the system level.

PERFORMANCE

Rather than using additional temperature compensation circui-try, innovative design techniques ensure that high performanceis built in to the ADXL335. As a result, there is no quantizationerror or nonmonotonic behavior, and temperature hysteresisis very low (typically less than 3 mg over the −25°C to +70°Ctemperature range).

Rev. 0 | Page 10 of 16

ADXL335

APPLICATIONS INFORMATION POWER SUPPLY DECOUPLINGFor most applications, a single 0.1 μF capacitor, CDC, placed close to the ADXL335 supply pins adequately decouples the accelerometer from noise on the power supply. However, in applications where noise is present at the 50 kHz internal clockfrequency (or any harmonic thereof), additional care in power supply bypassing is required because this noise can cause errors in acceleration measurement.

If additional decoupling is needed, a 100 Ω (or smaller) resistoror ferrite bead can be inserted in the supply line. Additionally, a larger bulk bypass capacitor (1 μF or greater) can be added in parallel to CDC. Ensure that the connection from the ADXL335 ground to the power supply ground is low impedance because noise transmitted through ground has a similar effect to noise transmitted through VS.

SETTING THE BANDWIDTH USING CX, CY, AND CZ

The ADXL335 has provisions for band limiting the XOUT, YOUT, and ZOUT pins. Capacitors must be added at these pins to imple-ment low-pass filtering for antialiasing and noise reduction. The equation for the 3 dB bandwidth is

F−3 dB = 1/(2π(32 kΩ) × C(X, Y, Z))

or more simply

F–3 dB = 5 μF/C(X, Y, Z)

The tolerance of the internal resistor (RFILT) typically varies as much as ±15% of its nominal value (32 kΩ), and the bandwidthvaries accordingly. A minimum capacitance of 0.0047 μF for CX, CY, and CZ is recommended in all cases.

Table 4. Filter Capacitor Selection, CX, CY, and CZ

Bandwidth (Hz) Capacitor (μF)

1 10 50 100 200 500

4.7 0.47 0.10 0.05 0.027 0.01

SELF-TEST

The ST pin controls the self-test feature. When this pin is set to VS, an electrostatic force is exerted on the accelerometer beam. The resulting movement of the beam allows the user to test if the accelerometer is functional. The typical change in outputis −1.08 g (corresponding to −325 mV) in the X-axis, +1.08 g (or +325 mV) on the Y-axis, and +1.83 g (or +550 mV) on the Z-axis. This ST pin can be left open-circuit or connected tocommon (COM) in normal use.

Never expose the ST pin to voltages greater than VS + 0.3 V. If this cannot be guaranteed due to the system design (for instance, if there are multiple supply voltages), then a low VF clamping diode between ST and VS is recommended.

DESIGN TRADE-OFFS FOR SELECTING FILTER CHARACTERISTICS: THE NOISE/BW TRADE-OFF

The selected accelerometer bandwidth ultimately determines the measurement resolution (smallest detectable acceleration).Filtering can be used to lower the noise floor to improve the resolution of the accelerometer. Resolution is dependent on the analog filter bandwidth at XOUT, YOUT, and ZOUT.

The output of the ADXL335 has a typical bandwidth of greaterthan 500 Hz. The user must filter the signal at this point to limit aliasing errors. The analog bandwidth must be no more than half the analog-to-digital sampling frequency to minimizealiasing. The analog bandwidth can be further decreased to reduce noise and improve resolution.

The ADXL335 noise has the characteristics of white Gaussian noise, which contributes equally at all frequencies and is described in terms of μg/√Hz (the noise is proportional to the square root of the accelerometer bandwidth). The user should limit bandwidth to the lowest frequency needed by the applica-tion to maximize the resolution and dynamic range of the accelerometer.

With the single-pole, roll-off characteristic, the typical noise ofthe ADXL335 is determined by

rms Noise Noise Density ( BW 1.6 )

It is often useful to know the peak value of the noise. Peak-to-peak noise can only be estimated by statistical methods. Table 5 is useful for estimating the probabilities of exceeding various peak values, given the rms value.

Table 5. Estimation of Peak-to-Peak Noise

Peak-to-Peak Value% of Time That Noise Exceeds Nominal Peak-to-PeakValue2 ×

rms 4× rms6 ×rms 8

32 4.6 0.27 0.006

USE WITH OPERATING VOLTAGES OTHER THAN 3 V

The ADXL335 is tested and specified at VS = 3 V; however, it can be powered with VS as low as 1.8 V or as high as 3.6 V. Note that some performance parameters change as the supply voltageis varied.

Page 11 of 16

ADXL335The ADXL335 output is ratiometric, therefore, the output sensitivity (or scale factor) varies proportionally to the supply voltage. At VS = 3.6 V, the output sensitivity is typi-cally 360 mV/g. At VS = 2 V, the output sensitivity is typically 195 mV/g.

The zero g bias output is also ratiometric, thus the zero g output is nominally equal to VS/2 at all supply voltages.

The output noise is not ratiometric but is absolute involts; therefore, the noise density decreases as the supplyvoltage increases. This is because the scale factor (mV/g)increases while the noise voltage remains constant. At VS

= 3.6 V,the X-axis and Y-axis noise density is typically 120 μg/√Hz, whereas at VS = 2 V, the X-axis and Y-axis noise density is typically 270 μg/√Hz.

Self-test response in g is roughly proportional to the square of the supply voltage. However, when ratiometricity of sensitivity is factored in with supply voltage, the self-test response in volts is roughly proportional to the cube of the supply voltage. For example, at VS = 3.6 V, the self-test response for the ADXL335is approximately −560 mV for the X-axis, +560 mV for the

Y-axis, and +950 mV for the Z-axis.

At VS = 2 V, the self-test response is approximately −96 mVfor the X-axis, +96 mV for the Y-axis, and −163 mV for the Z-

axis.

The supply current decreases as the supply voltage decreases. Typical current consumption at VS = 3.6 V is 375 μA, and typi-cal current consumption at VS = 2 V is 200 μA.

AXES OF ACCELERATION SENSITIVITYAZ

Figure 23. Axes of Acceleration Sensitivity; Corresponding OutputVoltage Increases When Accelerated Along the Sensitive Axis.

XOUT = –1g YOUT = 0g ZOUT = 0g

TOP

GRAVITY

XOUT = 0gYOUT = 1g TOPZOUT = 0g

XOUT = 0g TOP YOUT = –1g

ZOUT = 0g

TOP

XOUT = 1gYOUT = 0gZOUT = 0g

XOUT = 0gYOUT = 0gZOUT = 1g

Figure 24. Output Response vs. Orientation to Gravity

XOUT = 0gYOUT = 0gZOUT = –1g

Rev. 0 | Page 12 of 16

ADXL335

LAYOUT AND DESIGN RECOMMENDATIONS

The recommended soldering profile is shown in Figure 25 followed by a description of the profile features in Table 6. The recommended PCB layout or solder land drawing is shown in Figure 26.

TSMAX

RAMP-UP

CRITICAL ZONETL TO TP

TSMIN

tSPREHEAT

RAMP-DOWN

t25°C TO PEAK

TIME

Figure 25. Recommended Soldering Profile

Table 6. Recommended Soldering Profile

Profile Feature Sn63/Pb37 Pb-Free

Average Ramp Rate (TL to TP) Preheat